The advent of integrated circuitry has given rise to the need for integrated circuit packages that will both house and protect the integrated circuit die. These integrated circuit packages provide a mechanism for making electrical interconnection between the circuits on the integrated circuit die and the leads that are utilized to make electrical interconnections to circuits, power, and ground external to the integrated circuit die. In the early stages of development of integrated circuits, there were relatively few connections between the integrated circuit die and the external circuitry.
As integrated circuit packages provide electrical interconnection of integrated circuits to an electronic system at a next level of integration or hierarchy, a leadframe is one common means of electrical interconnection. The leadframe is formed from electrically conductive material, which is formed into leads. The lead ends are electrically connected to the integrated circuit die and the next level electronic system including external circuitry such as a printed circuit board. The leadframe also often include a die attach paddle to mount the integrated circuit die.
For those early types of integrated circuits, the interconnection to the integrated circuit package was relatively straightforward and generally involved an array of leads arranged around a die cavity to be electrically connected to associated die pads. There were also relatively few circuits on each integrated circuit die, and the circuit operational rates were by modern day standards relatively slow. Accordingly, the spacing and configuration of the leads with respect to the die pads was relatively less important in the consideration of the length of interconnection conductors and the degree of difficulty of reliable assembly.
Across virtually all applications, there continues to be growing demand for reducing size and increasing performance of integrated circuits. The seemingly ceaseless constrictions in requirement are no more visible than with products in our daily lives. Smaller and denser integrated circuits are required in many portable electronic products, such as cell phones, portable computers, voice recorders, etc. as well as in many larger electronic systems, such as cars, planes, industrial control systems, etc. As the demand grows for smaller electronic products with more features, manufacturers are seeking ways to reduce the size of the packaged integrated circuits. To meet these needs, packaging technologies are increasingly using smaller area designs with smaller features.
As the integrated circuit technology advanced, more circuit cells were able to be fabricated in a similar die area so that substantially increased functionality could be accomplished on a given integrated circuit die. The added functionality and increase in the number of circuits involved generally required a larger number of discrete connections to the associated external circuitry. As physical sizes decreased and the number of required die pads increased, it was necessary to develop integrated circuit packages that would accommodate connections to a larger number of leads. Both integrated circuit users and integrated package manufacturers worked to develop die interconnect systems that would accommodate the higher die pad densities.
Lead systems provide the connection of an integrated circuit chip to a next level system, such as a circuit board or an electronic device. These external connections cannot be made directly to an integrated circuit die due to the thin and fragile nature of the electrical connections within the integrated circuit die. Instead, a system of conductive package leads is provided to access the external connections. The integrated circuit die is connected or bonded to the leads using thin and flexible wires or bond wires.
An integrated circuit package generally includes a protective housing, which surrounds the integrated circuit die. The protective housing is usually filled with a liquid potting mixture, or other encapsulant, which then hardens in situ. During the introduction of the liquid, however, the bond wires are susceptible to mid-line motion or “sweep”. As the fill liquid is introduced across the wires from a given direction, the bond wires, which are parallel to the liquid flow, are minimally disturbed. However, the bond wires, which are perpendicular to (or across) the flow of the liquid, are easily bent out of position along the curve of the wires. Closely spaced adjoining bond wires can be “swept” into a position in which they touch. As the liquid fill material solidifies, the touching bond wires can provide a permanent short-circuit of the integrated circuit package, causing the integrated circuit package to fail.
A variety of approaches has been put forward to minimize or eliminate the bond wire “sweep”. The direction of the fill material entry (“center gating” and “side gating”, for example) has been varied to minimize sweep. Previous attempts with bonding patterns and systems have not provided an adequate bonding pattern to minimize shorting during fill processes. Specifically, prior art wire bonds tend to short during fill procedures when closely positioned adjacent wires touch.
The necessary bonding process also introduces potential short-circuit of the integrated circuit package. The bonding process creates bump balls on the leads that often extends beyond the leads to which the bump balls are attached. The bump balls are formed to attach the wire bonds to the package leads. The formation of the bump balls leaves a large deposition of the wire bond material on the package leads that tend to short with adjacent bump balls. The touching of adjacent bump balls can provide a permanent short-circuit of the integrated circuit package, causing the integrated circuit package to fail.
Thus, a need still remains for an integrated circuit package system to provide improved reliability and manufacturing yield with smaller features in a smaller area. In view of the increasing demand for improved density of integrated circuits and particularly portable electronic products, it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.